Integrated circuit having a coplanar solder ball contact array

Abstract

An integrated circuit includes a plurality of solder balls arrayed on the bottom surface of a package of the integrated circuit. These solder balls provide for surface mounting of the integrated circuit to a circuit board by solder reflow. The array of solder balls can be planarized so that each of the plural solder balls participate in defining a truly planar solder ball contact array for the integrated circuit package. Methods of manufacturing the integrated circuit with a package having planarized solder balls in an array dependent from a bottom surface thereof are set forth. The truly planarized solder ball contact array of the integrated circuit package affords nearly absolute reliability in forming of surface-mount electrical connections between the integrated circuit package and the circuit board on which the package is to mount. Additionally, the planarized solder ball contacts locally compensate individually for warpage of the integrated circuit package by variation in the individual dimensions of dependency of each solder ball below the bottom surface of the package.

We claim: 
     
       1. A method of making an integrated circuit including a package with a plurality of electrical contacts exposed on a bottom surface of said package for electrical interface of said integrated circuit with external electrical circuitry, said method comprising the steps of: providing a respective plurality of solder ball contact members dependent from said plural electrical contacts and said bottom surface of said package;   cooperatively defining with said plurality of solder balls a solder ball contact array plane;   engaging at least some individual solder balls of said plurality of solder ball contacts with a planar member to reshape said contacted solder balls;   utilizing said reshaping of said contacted solder balls to make said solder ball contact array plane substantially planar;   using as said planar member a strong platen with a planar surface against which said solder balls are contacted, and forcefully engaging said integrated circuit with said platen member to plastically distort and reshape said contacted solder balls; and   using a vacuum chuck member to hold said integrated circuit package during reshaping of said contacted solder balls.   
     
     
       2. The method of claim 1 additionally including the step of using said reshaping said contacted solder balls to locally compensate for warpage of said package. 
     
     
       3. The method of claim 1 additionally including the step of using said reshaping of said contacted solder balls to effect participation in said substantially planar contact array plane of each individual solder ball in said plurality of solder balls. 
     
     
       4. The method of claim 1 further including the step of configuring said vacuum chuck to also transfer force to said package for effecting said reshaping of said contacted solder balls. 
     
     
       5. The method of claim 4 additionally including the step of including in said vacuum chuck a resilient member effective to both sealingly engage with said package and retain the latter in engagement with said vacuum chuck under the effect of applied vacuum, and also to cushion said package during transfer of force to said package to effect reshaping of said contacted solder balls. 
     
     
       6. The method of claim 4 further including the step of including in said vacuum chuck a means for angular adjusting the position of said package member relative to said platen member surface. 
     
     
       7. The method of claim 6 wherein said step of including angular position adjusting means in said vacuum chuck includes the step of including a ball socket joint in said vacuum chuck. 
     
     
       8. The method of claim 1 further including the step of heating said planar member, and engaging said package with said planar member at said plurality of solder balls for a time and with said planar member at a temperature sufficient to effect softening and deformation of said contacted solder balls. 
     
     
       9. The method of claim 8 further including the step of using as said planar member a platen including a means for controllably heating said platen to a selected temperature. 
     
     
       10. The method of claim 9 additionally including the step of providing a surface on said platen against which said solder balls are engaged for deformation and which is not wetted by the solder of said solder balls.